1. Field of the Invention
The present invention relates to a liquid crystal display module, and particularly to a liquid crystal display module provided with a removable lamp unit structure.
2. Description of the Related Art
As thin display devices with low power consumption, liquid crystal display (LCD) devices have been widely used for display monitors, displays for personal computer, and displays for portable devices such as cellular phones and personal digital assistants (PDAs). LCD devices are generally provided in a module configuration in which an LCD panel, a back light unit and the like are integrated, and these LCD devices are incorporated into set products by set makers.
A structure of such an LCD module is briefly described. An LCD module is configured by housing an LCD panel and a back light unit together. The back light unit includes a fluorescent lamp, a lamp holder which holds the fluorescent lamp, and which has a function as a light reflector plate for reflecting light from the fluorescent lamp. A housing case of the LCD module is provided with an opening such that the lamp holder of the lamp unit is structured so as to be plugged into the LCD module through the opening. By plugging the lamp holder into the opening, the light guide plate, which is placed in a space surrounded by the housing case, and the fluorescent lamp of the lamp unit are aligned. By turning on the fluorescent lamp, light therefrom is directed to the light guide plate so that light of the back light is supplied from the light guide plate to the LCD panel. Moreover, the lamp unit is mounted on the LCD module so that the lamp unit is detachable from the LCD module. Thereby, in a case where the fluorescent lamp is replaced by new one due to life-time or a defect, each unit can be exchanged easily.
Incidentally, consideration will be made for a case where the LCD module as described above is incorporated into a set product such as a laptop computer or an LCD monitor. A connector of the lamp unit, which is provided to a lamp cable, is connected to a connecting terminal on the set product. Thereby, a drive voltage is supplied from the set product. Accordingly, the fluorescent lamp of the lamp unit is turned on.
Due to convenience in designing of the set product, there are cases where the connecting terminal of the set product for supplying the drive voltage is placed at the side not near but far from an output port for the lamp cable of the LCD module. In such cases, to connect the connector of the lamp unit to the connecting terminal on the set product, it is necessary to extend one of the lamp cable, and an inverter cable, of the lamp unit so that the cable is long enough to reach the connecting terminal of the set product and to be connected to the connecting terminal on the set product. In a case where extension of the lamp cable or the inverter cable is not desired, in order to connect the connector of the lamp unit to the connecting terminal of the set product, it is considered that the LCD module is rotated 180 degrees to be placed and connected to the connecting terminal of the set product.
However, the extension of the lamp cable as well as the rotation and placement of the LCD module may change characteristics, such as display characteristics or electric characteristics, of the LCD module. For example, when the lamp cable is extended, electric leak from the lamp cable is increased, and luminance of the lamp may decrease. Furthermore, when the LCD module is placed by rotating thereof, display characteristics, such as view angle characteristic, gradation characteristics, color, in-plane luminance distribution and the like, are changed. For this reason, desirable display characteristics may not be obtained.